Potentiating herbicidal compositions of auxin transport inhibitors and phenoxy butyric acid herbicides

ABSTRACT

The present invention is directed to the use of certain auxin transport inhibiting semicarbazones to potentiate the herbicidal activity of other herbicides. The present invention includes potentiating herbicidal compositions of these auxin transport inhibitors and growth regulator herbicides and particularly phenoxy butyric acid herbicides. These potentiating herbicidal compositions have been found especially useful in combating or controlling the growth of broadleaf weeds, especially when applied postemergence to the locus of these weeds.

This application is a division of application Ser. No. 08/400,420, filedMar. 3, 1995, now U.S. Pat. No. 5,665,673, which is a continuation ofapplication Ser. No. 08/156,503, filed Nov. 23, 1993, now abondoned,which is a continuation-in-part of application Ser. No. 07/972,056,filed Nov. 5, 1992, now abandoned, which is a continuation ofapplication Ser. No. 07/704,684, filed May 17, 1991, now abandoned,which is a continuation of application Ser. No. 07/490,792 filed Mar. 8,1990, now abandoned, which is a continuation-in-part of application Ser.No. 07/291,850, filed Dec. 29, 1988, now abandoned.

The present invention concerns the use of auxin transport inhibitors aspotentiators or enhancers of herbicides, as well as co-application ofsuch auxin transport inhibitors and herbicides, compositions containingat least one auxin transport inhibitor in combination with at least oneherbicide and use of these in combatting or controlling undesired plantgrowth and in plant growth regulation.

Auxin transport inhibitors are compounds which themselves are herbicidesand act by inhibiting transmembrane movement of auxin which accumulatesin the cells and affects plant growth. Examples of auxin transportinhibitors are e.g. naptalam, TIBA and DPX 1840 (cf E. M. Beyer, Jr.Plant Physiol., 50, 322 (1972), E. M. Beyer, Jr. et al., Plant Physiol.,57, 839 (1976)) and semicarbazones such as described in U.S. Pat. Nos.5,098,462 and 5,098,466 and EP Patent 219,451. Especially preferredauxin transport inhibitors in the practice of the invention arecompounds of formula A: ##STR1## wherein, X and Y representindependently, hydrogen, fluorine or chlorine, and

R is the group ##STR2## wherein Z is hydrogen, fluorine or chlorine andM is hydrogen, or a salt forming moiety e.g. an alkali metal cation oran optionally substituted ammonium cation.

Compounds of formula A are generally disclosed, e.g. in U.S. Pat. Nos.5,098,462 and 5,098,466and in European Patent No. 219,451, as well asprocesses for their production, their use as herbicides and plant growthregulators and herbicidal and plant growth regulating compositionscontaining them, the contents of each of which in this respect areincorporated herein by reference. These patents make no reference to thespecific compound group of formula A or its potentiating activity.

The term herbicides, as used herein, refers to compounds which combat orcontrol undesired plant growth. This class of compounds may be dividedinto subclasses according to the primary type or mode of action theherbicide has on the plant. For example according to G. F. Warren ofPurdue University, Ind., USA, herbicides can be classified as auxintransport inhibitors, growth regulator herbicides, photosynthesisinhibitors, pigment inhibitors, growth inhibitors, amino acid synthesisinhibitors, lipid biosynthesis inhibitors, cell wall biosynthesisinhibitors, rapid cell membrane disruptors as well as "miscellaneous"herbicides which do not come under one of the preceding categories.(Growth regulator herbicides include, e.g. auxin agonists.)

In accordance with the present invention it has now surprisingly beenfound that auxin transport inhibitors, which are usually highly activeherbicides in their own right, potentiate the activity of otherherbicides on co-application therewith. In the context of this inventionherbicides are to be understood as including desiccants and defoliants.

Potentiating, as herein used, refers to the interaction of the auxintransport inhibitor with the herbicide such that the activity is greaterthan the predicted activity, based upon the activity observed for theauxin transport inhibitor and the herbicide separately. Thus,co-application results in herbicidal activity which is significantlysuperior to the additive effectiveness of the individual activesubstances.

This potentiation manifests itself in various forms. Thus,co-application enables application rates to be employed for the auxintransport inhibitor(s) and/or herbicide(s) which would be insufficientlyeffective if employed alone, or enables various types of weeds to becontrolled which would not be controlled by application of eachindividual active ingredient alone at the same rates as in the mixture.

Furthermore, co-application results in herbicidal activity which issignificantly superior to the additive effectiveness of the individualactive substances. Moreover, the auxin transport inhibitors of thisapplication are able to increase the efficacy of a herbicide such thatthe maximum level of control or growth regulation for a givenapplication rate of a herbicide is increased, or alternatively, theapplication rate of a herbicide giving optimum control or growthregulation can be reduced.

Under co-application is to be understood concurrent, or immediatelysequential application (e.g. within 24 hours), application as a tank mixor application of fixed combination preniixes.

Non-limiting examples of herbicides which may be potentiated by use ofauxin transport inhibitors, especially compounds of formula A inaccordance with the invention include

1. other auxin transport inhibitors, e.g. naptalam;

2. growth regulators, including 1) benzoic acids, e.g. dicamba; b)phenoxy acids i) acetic acid type, e.g. 2,4-D, MCPA, ii) propionic acidtype, e.g. 2,4-DP, MCPP, iii) butyric acid type, e.g. 2,4-DB, MCPB; c)picolinic acids and related compounds, e.g. picloram, triclopyr,fluroxypyr, clopyralid;

3. photosynthesis inhibitors, including a) s-triazines i) chlorosubstituted, e.g. atrazine, simazine, cyanazine, ii) methoxysubstituted, e.g. prometon, iii) methylthio substituted, e.g. ametryn,prometryn; b) other triazines, e.g. hexazinone, metribuzin; c)substituted ureas, e.g. diuron, fluometruon, linuron, tebuthiuron,thidiazuron, forchlorfenuron; d) uracils, e.g. bromacil, terbacil; e)others, e.g. bentazon, desmidepham, methazole, phenmedipham, propanil,pyrazon, pyridate;

4. pigment inhibitors, including a) pyridazinones, e.g. norflurazon; b)isoxazolones, e.g. clomazone; c) triketones and cyclic diones of thetype described in U.S. Pat. Nos. 4,695,673; 4,921,526; 5,006,150;5,089,046, U.S. patent application Ser. No. 07/411,086 now U.S. Pat. No.5,801,120 (and EP 338,992); and 07/994,048 now U.S. Pat. No. 5,336,662(and EP 394,889 and EP 506,907) the contents of each of which areincorporated herein by reference including for example2-(2-chloro-4-methylsulfonylbenzoyl)-1,3-cyclohexane dione (akasulcotrione);2-(4-methylsulfonyloxy-2-nitrobenzoyl)-4,4,6,6-tetramethyl-1,3-cyclohexanedione;3-(4-methylsulfonyloxy-2-nitrobenzoyl)-bicyclo 3,2,1!octane-2,4-dione;3-(4-methylsulfonyl-2-nitrobenzoyl)-bicylco 3,2,1!octane-2,4-dione;4-(4-chloro-2-nitrobenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H,6H)dione;4-(4-methylthio-2-nitrobenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H,6H)-dione;3-(4-methylthio-2-nitro-benzoyl)-bicyclo3,2,1!octane-2,4-dione;4-(2-nitro-4-trifluoromethoxybenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H,6H)-dione;d)others,e.g.amitrole, fluridone;

5. growth inhibitors, including a) mitotic disruptors i)dinitroanilines, e.g. trifluralin, prodiamine, benefin, ethalfluralin,isopropalin, oryzalin, pendimethalin; ii) others, e.g. DCPA, dithiopyr,thiazopyr, pronamide; b) inhibitors of shoots of emerging seedlings i)thiocarbamates, e.g. EPTC, butylate, cycloate, molinate, pebulate,thiobencarb, triallate, vemolate; c) inhibitors of roots only ofseedlings, e.g. bensulide, napropamide, siduron; d) inhibitors of rootsand shoots of seedlings, including chloroacetamides e.g. alachlor,acetochlor, metolachlor, diethatyl, propachlor, and thiophenamines suchas dimethenamid (a.k.a. 2-chloro-N-1-methyl-2-methoxy-ethyl!-N-(2,4-dimethyl-thien-3-yl)acetamide; cf U.S.Pat. No. 4,666,502), and others e.g. cinmethylin;

6. amino acid synthesis inhibitors, including a) glyphosate; glufosinateb) sulfonylureas, e.g. metsulfuron, metsulfuron-methyl, ethametsulfuron,nicosulfuron, triasulfuron, primisulfuron, bensulfuron, chlorimuron,chlorimuron-ethyl, chlorsulfuron, sulfometuron, thifensulfuron,tribenuron, triflusulfuron, clopyrasulfuron and pyrazasulfuron; c)sulfonamides, e.g. flumetsulam (a.k.a. DE498); d) imidazolinones, e.g.imazaquin, imazamethabenz, imazapyr, imazethapyr;

7. lipid biosynthesis inhibitors, including a) cyclohexanediones, e.g.sethoxydim, clethodim; b) aryloxyphenoxys, e.g. fluazifop-P-butyl,diclofop-methyl, haloxyfopmethyl, quizalofop; c) others, e.g.fenoxaprop-ethyl;

8. cell wall biosynthesis inhibitors, e.g. dichlobenil, isoxaben;

9. rapid cell membrane disruptors, including a) bipyridiliums, e.g.paraquat, diquat; b) diphenyl ethers, e.g. acifluorfen, fomesafen,lactofen, oxyfluorfen; c) glutamine synthetase inhibitors, e.g.glufosinate; d) others, e.g. oxadiazon;

10. miscellaneous, including a) carbamates, e.g. asulam; b) nitriles,e.g. bromoxynil, ioxynil; c) hydantocidin and derivatives; d) various,e.g. paclobutrazol, ethofumesate, quinclorac (a.k.a. BAS514),difenzoquat, endothall, fosamine, DSMA, MSMA;

11. Others

Compounds of the type described in EP 315889 and U.S. patent applicationSer. No. 07/804,150 now abandoned (and EP 461,079 and EP 549,524); andPCT Appln. No. 91/10653 the contents of each of which are incorporatedherein by reference including for example 3-(4,6-dimethoxy-2-pyrimidinyl)hydroxymethyl!-N-methyl-2-pyridinecarboxamide;4,7-dichloro-3-(4,6-dimethoxy-2-pyrimidinyl)-3-hexanoyloxyphthalide;3-(4,6-dimethoxy-2-pyrimidinyl)carbonyl!-N,N-dimethyl-2-pyridinecarboxamide;3,6-dichloro-2-(4,6-dimethoxy-2-pyrimidinyl)carbonyl!benzoicacid; 6-chloro-2-(4,6-dimethoxy-2-pyrimidinyl)thio!benzoic acid (aka DPX-PE350 orpyrithiobac) and salts thereof.

It will be noted that in some cases one auxin transport inhibitor maypotentiate the effect of another. The nature of the effect of the auxintransport inhibitor is such that it has the potential to enhance theactivity of different classes of herbicides.

The present invention therefore also concerns a method of combatting orcontrolling undesired plant growth or otherwise regulating plant growthwhich comprises co-applying to a locus where such combatting or controlis desired an herbicidally or plant growth regulating effectiveaggregate amount of at least one auxin transport inhibitor and at leastone other herbicide, wherein the auxin transport inhibitor is applied ata potentiating rate.

Application rates for co-application will of course vary depending uponclimatic conditions, season, soil ecology, weeds to be combatted and thelike, however, successful results can be obtained e.g. with rates ofauxin transport inhibitor of 0.00011 kg to 1.1 kg/ha (0.0001 lb to 1.0lb/A), preferably 0.0011 to 0.55 kg/ha (0.001 to 0.5 lb/A), especially0.011 to 0.11 kg/has (0.01 to 0.1 lb/A) in co-application with rates forpartner herbicides which correspond to or are significantly lower thanrecommended for use thereof individually (application rates hereinafterset forth are calculated from measurements originally made in lb/A usingthe conversion factor 1 lb/A=1.1 kg/ha).

The suitability of specific co-applications for pre- or post-emergentuses and selectivity will of course depend on the partners chosen.

The activity of compounds of formula A is described in the abovementioned patents and that of other known auxin transport inhibitors andof suitable herbicidal partners is described in the literature or oncommercially available forms thereof (cf also CROP PROTECTION CHEMICALSREFERENCE, Chemical & Pharmaceutical Press, N.Y., N.Y.).

The invention also provides herbicidal or plant growth regulatingcompositions comprising at least one auxin transport inhibitor and atleast one other herbicide, wherein the auxin transport inhibitor ispresent in a potentiating amount. Especially preferred compositionscontain a compound of formula A.

Such compositions contain the active substances in association withagriculturally acceptable diluents. They may be employed in either solidor liquid forms e.g. in the form of a wettable powder or an emulsifiableconcentrate, incorporating conventional diluents. Such compositions maybe produced in conventional manner, e.g. by mixing the active ingredientwith a diluent and optionally other formulating ingredients such assurfactants and oils.

The term diluents as used herein means any liquid or solidagriculturally acceptable material which may be added to the activeconstituent to provide a more easily or improved applicable form, or toachieve a usable or desirable strength of activity. Examples of diluentsare talc, kaolin, diatomaceous earth, xylene, non-phytotoxic oils, orwater.

Particular formulations, to be applied in spraying forms such as waterdispersible concentrates, water dispersible granules, or wettablepowders, may contain surfactants such as wetting and dispersing agents,e.g. the condensation product of formaldehyde with naphthalenesulphonate, an alkylarylsulphonate, a lignin sulphonate, a fatty alkylsulphate, an ethoxylated alkylphenol, a Urea/Ammonium Nitrate mix, amethylated vegetable oil (e.g. SCOIL®--Agsco Inc., Grand Ford, N.Dak.),an alkylpolyoxyethylene glycol (e.g. X77-Valent, Walnut Creek, Calif.) abuffered crop oil (e.g. DASH®, BASF Corp., Parsippanny, N.J.) or anethoxylated fatty alcohol.

In general, the formulations include from 0.01 to 90% by weight ofactive agent(s) and from 0 to 20% by weight of agriculturally acceptablesurfactant, the active agent consisting either of at least one auxintransport inhibitor and at least one other herbicide. Concentrate formsof compositions generally contain between about 2 and 90%, preferablybetween about 5 and 80% by weight of active agent. Application forms offormulation may for example contain from 0.01 to 20% by weight of activeagent.

When employing concurrent, immediately sequential or tank mixapplications the non-auxin transport inhibitor partner(s) can beemployed in commercially available form if appropriate and at ratesequivalent to or preferably below those recommended by the manufacturer.The auxin transport inhibitor can be formulated as described in theabove mentioned EP 219,451, U.S. Pat. No. 5,098,462 or 5,098,466.

On co-application according to the present invention other compoundshaving biological activity, e.g. compounds having insecticidal orfungicidal activity, may also be included.

The preferred modes of application include tank mix prepared e.g. byadding an auxin transport inhibitor to a tank containing the otherherbicide partner and an appropriate surfactant and fixed combinationpremixes.

Depending on the choice of co-application partners both pre- andpost-emergent activity on a large range of broadleaf and grassy weedsmay be achieved. Non-limiting examples of such weeds are

Setaria sp.--foxtail

Brachiaria platvphvlla--broadleaf signalgrass

Ipomoea sp.--morningglories

Abutilon theophrasti--velvetleaf

Hibiscus trionum--Venice mallow

Solanum sp.--nightshades e.g. silverleaf nightshade

Avena fatua--wild oats

Sinapis alba--white mustard

Amaranthus sp.--pigweeds, spiny amaranth

Xanthium strumarium--common cocklebur

Sorghum halepense--johnsongrass

Echinochloa crus-galli--bamyardgrass

Polygonum sp.--smartweeds, wild buckwheat, prostrate knotweed

Cassia obtusifolia--sicklepod

Digitaria sp.--e.g. crabgrasses

Bromus tectorum--downy brome

Apera spica-venti--windgrass

Chenopodium album--common lambsquarter

Sorghum bicolor--shattercane

Portulaca oleracea--common purslane

Sida spinosa--prickly sida

Campsis radicans--trumpet creeper

Rottboellia exaltata--itchgrass

Cynodon dactylon--bermudagrass

Agropyron repens--quackgrass

Cyperus sp.--nutsedges

Panicum sp. e.g.--prosomillet

Lespedeza sp--lespedezas

Trifolium sp.--clovers

Hippuris vulgaris--marestail

Asclepias sp--milkweeds

Salvia sp--e.g. lanceleaf sage

Salsola iberica--russian thistle

Convolvulus arvensis--field bindweed

Cirsium arvense--Canada thistle

Proboscidea louisianica--devilsclaw

Senecio sp.--common groundsel

Chorispora tennela--blue mustard

Alopecurus mvosuroides--blackgrass

Sisvmbrium altissimum--tumble mustard

Caperionia palustris--texasweed

Crop selectivity will also usually depend upon choice of partners.Compounds of formula A for example exhibit excellent selectivity in cornand small grain crops and can also be used in turf and fallowapplications.

It will be appreciated that mixtures of an auxin transport inhibitorwith more than one other herbicide, e.g. 3-way mixes, are alsocontemplated.

Preferred auxin transport inhibitors are those of formula A especiallythose wherein M is hydrogen or a sodium, potassium, isopropylammonium or2-(2-hydroxyethoxy)ethylammonium cation (Compounds A₁).

Other compound groups comprise compound of formula A wherein Zrepresents hydrogen (compounds A2); Z represents fluorine (compoundsA3); Z represents chlorine (compounds A4).

Particularly preferred individual auxin transport inhibitors are2-acetylnicotinic acid 4-(3,5-difluorophenyl)semicarbazone in free acidor in salt form especially its sodium salt form, 2-acetylnicotinic acid4-(3-fluorophenyl)semicarbazone in free acid form or in salt formespecially in sodium salt form, and 2-acetylnicotinicacid-4-(3-chlorophenyl)semicarbazone in free acid form or in sodium saltform.

Preferred classes of herbicidal mix partners are growth regulatorherbicides, such as benzoic acids, phenoxy acetic acids, picolinic acidsand related compounds, growth inhibitors such as inhibitors of roots andshoots of seedlings, rapid cell membrane disruptors such asbipyridiliums, amino acid synthesis inhibitors such as sulfonylureas andsulfonamides.

Examples of specific, preferred herbicidal partners for co-applicationare selected from dicamba, thidiazuron, 2,4-D, dimethenamid, atrazine,cyanazine, norflurazon, fluroxypyr, primisulfuron, nicosulfuron,triclopyr, picloram, MCPA, MCPP, pendimethalin, clopyralid, paraquat,ethofumesate, flumetsulam (a.k.a. DE498) and glyphosate.

Non-limiting examples of specific combinations are those containing e.g.2-acetylnicotinic acid 4-(3,5-difluorophenyl)semicarbazone2-(2-hydroxyethoxy)ethylammonium salt (a); or 2-acetylnicotinic acid,4-(3-fluorophenyl)semicarbazone sodium salt (b); or 2-acetylnicotinicacid 4-(3-chlorophenyl)semicarbazone sodium salt (c); 2-acetylnicotinicacid 4-(3,5-difluorophenyl)semicarbazone (d); 2-acetylnicotinic acid4-(3,5-difluorophenyl) semicarbazone sodium salt (e); each with e.g.dicamba (z); dimethenamid (y); 2,4-D (x); or thidiazuron (w).

As stated above, application rates may depend on a variety of factors.In general, satisfactory results are obtained when applying theco-application partners at the rates given below:

Compound (a), (b), (c) or (d) 0.0011 to 1.1 kg/ha preferably 0.011 to0.55 kg/ha, especially 0.011 to 0.11 kg/ha.

Compound (z) 0.011 to 2.2 kg/ha, preferably 0.05 to 0.55 kg/ha,especially 0.11 to 0.55 kg/ha.

Compound (y) 0.11 to 4.4 kg/ha, preferably 0.275 to 1.0 kg/ha,especially 0.55 to 1.0 kg/ha.

Compound (x) 0.011 to 2.2 kg/ha, preferably 0.11 to 1.1 kg/ha,especially 0.275 to 0.825 kg/ha.

Compound (w) 0.011 to 1.1 kg/ha, preferably 0.055 to 0.55 kg/ha,especially 0.088 to 0.44 kg/ha.

The weight ratio of individual components in fixed premixes will varyaccording to the intended application rate thus for example, the ratioof compound (a) to compound (z) in a premix may varv e.g. from 1:2000 to100:1, preferably 1:50 to 5:1, especially 1:50 to 1:1 e.g. 1:50 to1:2.5.

Examples of a 3-way mixtures are compound (e) with compound (z) andnicosulfuron, dimethenamid or glyphosate.

Also for example a mixture of compound (d) or a salt thereof withcompound (z) may have added thereto a grass active herbicide such asfrom classes 5 and 7 listed above.

The compounds of formula A wherein Z is chlorine or fluorine are new andalso form part of the invention. The invention therefore furtherconcerns compounds of formula XA ##STR3## wherein X, Y and M are asdefined for formula A and Z' represents chlorine or fluorine.

The invention also concerns use of compounds of formula XA alone or incombination with other active compounds in combatting weeds, herbicidalcompositions containing compounds of formula XA either alone or incombination with other active compounds and processes for preparingcompounds of formula XA.

Particular compounds of formula XA are for example those wherein X isfluorine or chlorine, Y is hydrogen or fluorine and Z is 6-fluorine or6-chlorine (ortho to carboxylic) in salt or free acid form.

Compounds of formula XAwherein Z' is 6-fluorine or 6-chlorine areparticularly preferred.

The use of compounds of formula XA and their formulation as herbicidalcompositions can be carried out as described herein or as described inU.S. Pat. Nos. 5,098,462; 5,098,466 and in European Patent No. 219,451,the contents of each of which in this respect are incorporated herein byreference.

The following examples are intended to illustrate without in any waylimiting the invention.

EXAMPLE 1 Field Test

A field trial was conducted against velvetleaf and pigweed in fieldcorn. Application was post-emergent 35 days after seeding with weeds ata height of 41 to 89 cm. Application was of tank mixed formulation byfoliar applied broadcast treatment. Compound (a) above was tank mixed asis. Compound (z) above was tank mixed in the form of a 0.5 kg/l s.c.commercially available under the trademark BANVEL®. Aquagene is acommercially available surfactant, (Universal Coop Incorporated,Minneapolis, Minn.). Values set forth are calculated from measurementsoriginally made in acres, lbs, inches and gallons according to theconversion factors: 1 hectare=2.47 acres; 1 kg=2.2 lbs;

1 m=3.28 ft; and 1 gallon=3.78 1.

The results may be summarized as follows.

    ______________________________________              Rate     % of control    Treatment   kg/ha      Velvetleaf                                    Pigweed    ______________________________________    Aquagene.sup.1                0          0        0    Compound (z)                0.275      18       30    Compound (a)                0.011      13       18    Compound (z) +                0.275      27       40    Aquagene.sup.1    Compound (a) +                0.011      13       18    Aquagene.sup.1    Compound (a) +                0.011      57       90    Compound (z)                0.275    Compound (a) +                0.011      65       93    Compound (z)                0.275    Aquagene.sup.1    ______________________________________     (.sup.1 0.9 l/ha)

The tank mix combination of (a) plus (z) was significantly better thaneither treatment alone. The adjuvant provided some increase in control,but was not responsible for the surprising increase in control observedfor the herbicide combination. The combination of (a) plus (z) yielded aresponse markedly superior to the additive effect of either herbicidewhich when applied alone at the stated rate showed unsatisfactory weedcontrol.

There was no significant effect on the field corn.

EXAMPLE 2 Greenhouse Test

A greenhouse test was conducted against velvetleaf, pigweed,morningglory and cocklebur. Treatment was at 10 days post-emergence andevaluation at 18 days after treatment. Compound (e) was formulated astechnical a.i. in a mixture of equal parts acetone and water with 1/2%surfactant. Compound (z) was used in the commercially available formBANVEL® herbicide (=480 g/L a.i. equivalent) in water with 1/2%surfactant. The tank mixes were applied in a linear spray chamber with 3repetitions per concentration.

    ______________________________________            Rate      % control                      Velvet-        Morning-    Treatment kg/ha   leaf    Pigweed                                     glory  Cocklebur    ______________________________________    Compound (e)              0.01    55      50     55     25    Compound (z)*              0.02    35      35     35     75    Compound (e) +              0.01    98      100    98     100    Compound (z)              0.02    ______________________________________     The results indicate synergism utilizing Limpel's formula and are     statistically significant utilizing Duncan's multiple range test.     *as the commercially available BANVEL ® herbicide.

EXAMPLE 3 Preparation of2-acetyl-6-fluorobenzoicacid4-(3.5-difluorophenyl)semicarbazone(Table Acpd 1)

a) Preparation of 3-fluorophthalic anhydride

15 g of 3-fluorophthalic acid are mixed with 16.6 g of acetic anhydrideand refluxed for 3 hrs. After removal of unreacted acetic anhydride theremaining white solid is recrystalized from toluene.

b) Preparation of 2-acetyl-6-fluorobenzoic acid

9 g of 3-fluorophthalic anhydride and 6.8 g of malonic acid are mixed in80 ml of triethylamine and heated in an oil bath at 71°-72° untilevolution of gas ceases. The reaction mixture is mixed with 50 ml of 10%HCl/H₂ O and extracted with ether. The ether is evaporated off and theresulting black oil chromatographed on a column using 1 l of 20% ofethylacetate/hexane followed by 1 l of 30% ethylacetate/hexane to yieldfirst the 3-fluoro-isomer followed by the desired 6-fluoro isomer; m.p.76°-81.5°.

c) Preparation of title compound

3 g of 6-fluoro-2-acetyl benzoic acid and 3 g of4-(3,5-difluorophenyl)-semicarbazide are mixed in 20 ml of methanol andheated until clear. The solution is then stirred at R.T. for 24 hr. Awhite solid forms which is filtered and dried in vacuum at 60° to yieldthe title product m.p. 227° (decomp.). The corresponding sodium salt ismade by reaction of the free acid with 25% sodium methoxylate/methanol.

The following compounds of formula XA may be prepared analogously.

                  TABLE A    ______________________________________    Cpd no   X     Y         Z'     m.p.    ______________________________________    1        F     F         6-F    acid 227° (decomp)                                    Na.sup.+ salt    2        F     H         6-F    acid 174° (decomp)    3        Cl    H         6-F    acid 157° (decomp)    4        F     F         6-Cl   acid 174° (decomp)    5        F     H         6-Cl   acid 176° (decomp)    6        Cl    H         6-Cl   acid 204° (decomp)    ______________________________________

What is claimed is:
 1. A herbicidal composition comprising aherbicidally effective aggregate amount of an auxin transport inhibitorof Formula A: ##STR4## wherein, X and Y represent independently,hydrogen, fluorine or chlorine, provided that at least one of X and Y isfluorine or chlorine, and R is selected from one of the groups: ##STR5##wherein Z is hydrogen, fluorine or chlorine and M is hydrogen or a saltforming moiety; and a phenoxy butyric acid herbicide; wherein the auxintransport inhibitor is present in an amount producing a potentiatingeffect.
 2. A herbicidal composition according to claim 1 wherein thephenoxy butyric acid herbicide is selected from the group consisting of2,4-DB and MCPB.
 3. A herbicidal composition according to claim 1wherein in the auxin transport inhibitor of formula A, M is hydrogen ora sodium, potassium, isopropylammonium or2-(2-hydroxyethoxy)ethylammonium cation.
 4. A herbicidal compositionaccording to claim 1 wherein the auxin transport inhibitor is2-acetylnicotinic acid 4-(3,5-difluorophenyl)semicarbazone,2-acetylnicotinic acid 4-(3-fluorophenyl)semicarbazone or2-acetylnicotinic acid 4-(3-chlorophenyl)semicarbazone in free acid orin salt form.
 5. A herbicidal composition according to claim 1 whereinthe auxin transport inhibitor is 2-acetylnicotinic acid4-(3,5-difluorophenyl)semicarbazone 2-(2-hydroxyethoxy) ethylammoniumsalt (a); 2-acetylnicotinic acid 4-(3-fluorophenyl)-semicarbazone sodiumsalt (b); 2-acetylnicotinic acid 4-(3-chlorophenyl)semicarbazone sodiumsalt (c); or 2-acetylnicotinic acid 4-(3,5-difluorophenyl)semicarbazone(d); and the phenoxy butyric acid herbicide is 2,4-DB or MCPB.
 6. Aherbicidal composition according to claim 1 wherein the weight ratio ofauxin transport inhibitor to phenoxy butyric acid herbicide is 1:2000 to100:1.
 7. A herbicidal composition according to claim 6 wherein theweight ratio of auxin transport inhibitor to phenoxy butyric acidherbicide is 1:50 to 5:1.
 8. A herbicidal composition according to claim7 wherein the weight ratio of auxin transport inhibitor phenoxy butyricacid other herbicide is 1:50 to 1:1.
 9. A herbicidal compositionaccording to claim 8 wherein the weight ratio of auxin transportinhibitor to phenoxy butyric acid herbicide is 1:50 to 1:2.5.
 10. Aherbicidal composition according to claim 1 wherein the R group offormula A is the pyridyl group.
 11. A method for combating orcontrolling undesired plant growth comprising co-applying postemergenceto a locus of a broadleaf weed, a herbicidally effective aggregateamount of an auxin transport inhibitor of Formula A: ##STR6## wherein, Xand Y represent independently, hydrogen, fluorine or chlorine, providedthat at least one of X and Y is fluorine or chlorine, and R is selectedfrom one of the groups: ##STR7## wherein Z is hydrogen, fluorine orchlorine and M is hydrogen or a salt forming moiety, and a phenoxybutyric acid herbicide, wherein the auxin transport inhibitor is presentin an amount producing a potentiating effect.
 12. A method according toclaim 11 wherein the auxin transport inhibitor is applied at a rate of0.0011 to 1.1 kg/ha.
 13. The method according to claim 11, wherein thephenoxy butyric acid herbicide is 2,4-DB or MCPB.
 14. The methodaccording to claim 11, wherein the R group of Formula A is the pyridylgroup.
 15. The method according to claim 11, wherein the auxin transportinhibitor is 2-acetylnicotinic acid 4-(3,5-difluorophenyl)semicarbazone2-(2-hydroxyethoxy) ethylammonium salt (a); 2-acetylnicotinic acid4-(3-fluorophenyl)-semicarbazone sodium salt (b); 2-acetylnicotinic acid4-(3-chlorophenyl)semicarbazone sodium salt (c); or 2-acetylnicotinicacid 4-(3,5-difluorophenyl)semicarbazone (d).
 16. The method accordingto claim 11, wherein said co-applying step comprises co-applying theherbicides to the locus of a broadleaf weed in a corn field.
 17. Amethod of potentiating the herbicidal effect of a phenoxy butyric acidherbicide comprising combining a phenoxy butyric acid herbicide with apotentiating effective amount of an auxin transport inhibitor of theformula: ##STR8## wherein X and Y represent independently, hydrogen,fluorine or chlorine, at least one of X and Y is fluorine or chlorine,and R is the group: ##STR9## wherein M is hydrogen or a salt formingmoiety, to produce a herbicidally effective composition.
 18. The methodaccording to claim 17, wherein the phenoxy butyric acid herbicide is2,4-DB or MCPB.